Psilocybin mushrooms or magic mushrooms are characterised by their spectacular blueing reaction when fruiting bodies of the fungus are bruised, injured or exposed to air. For years, scientists, amateurs and other mushroom enthusiasts have been intrigued by this natural phenomenon. Some recent studies finally shed new light on this mysterious blueing reaction. In magic mushrooms, psilocin is the psychoactive metabolite of the naturally produced psilocybin. Research from 2020  hypothesised that the blueing was primarily caused by a derivative of psilocin (the 5,5’-coupled quinone dimer of psilocin). In a cascade reaction, psilocybin is first degraded to psilocin upon which it is then degraded to the derivative responsible for the blue colour. Two new enzymes were identified which were held responsible for the colour reaction. New evidence did not support the original hypothesis anymore. In a new study , all sorts of psilocin derivatives were synthesised to provide stable analogues to conduct experiments on. These analogues were analysed to determine which compound produced to blue colour. Experimental and computational data concluded that a different derivative (the 7,7’-coupled dimer of psilocin) than first thought is responsible for the blue colour. With new evidence on the chemical aspect of the bluing reaction, the ecological advantage for psilocybin production in fungi still remains unclear. Two possible hypotheses remain discussed to this day:
A first interpretation is that the metabolite psilocin is a strong psychedelic substance that could protect the mushrooms from animal predators by altering their behaviour.
An alternative explanation posits that psilocin is produced from psilocybin as a ‘defence-on-demand’ mixture with ecological advantage for the fungus. The degraded psilocybin products formed upon injury could produce reactive oxygen species when ingested by insects. This would be due to the basic and oxidative environment in the animals' guts. The derivatives can thus form intestinal lesions in the insect intestines, which is supposedly a defence mechanism of psilocybin used by the fungus . At first, these discoveries don’t seem much to anyone except biologists. Findings like this however will become new stepping stones in the overall scientific understanding of our natural world and can kickstart further research and progress in psychedelic science. Novel questions arise for the potentially large-scale psilocybin mushroom cultivation with this new knowledge. If bluing decreases the potency of mushrooms by modifying psilocybin and psilocin to other compounds, how can this loss be minimised? Would freeze-drying be the solution to prevent it? Also, does bluing alter other physiological mechanisms in mushrooms than the colour change ?  C. Lenz, J. Wick, D. Braga, M. García-Altares, G. Lackner, C. Hertweck, M. Gressler, D. Hoffmeister, Angew. Chem. Int. Ed. 2020, 59, 1450.  C. Lenz, S. Dörner, A. Sherwood, D. Hoffmeister, Chem. Eur. J. 2021, 27, 12166.  B.E. Bauer (2021). More Details on the Psilocybin Mushroom Bluing Reaction. Psychedelic Science Review.